Microelectromechanical systems (MEMS) devices or computer chips are often mounted on dies. Stresses due to die mounting can affect the performance of MEMS devices. The stresses change with temperature because of the differing coefficients of thermal expansion (CTE) of the package and the die; dies made of silicon or borosilicate glass typically have a lower CTE than that of the package, so as temperature changes, the package stresses the die. Thus, as shown in FIGS. 1A and 1B, a die 10 with a lower CTE than a package 12 are heated when attaching the die 10 to the package 12. When the assembly 14 cools, the package experiences more shrinkage than the die, and creates stress at attachment points 16. The stress affects the performance of the MEMS device 9.
The stresses also change due to shock when wire bonds change shape, which causes problems for capacitive sensors that require stable geometry for stable output. Additionally, making wire bonds at the package level makes the parts more expensive because each part must be handled separately, as well as increasing the chance of damage to the assembly.